Universal pressure protector for a polish rod

ABSTRACT

Method and apparatus for protecting a wellhead drive assembly has a housing having a polish rod seal and utilizes standard flanges adapted to fit between the existing stuffing box of any wellhead drive assembly and the standard flange of a well for extending the longevity of the existing stuffing box. In another embodiment, the housing, with or without a polish rod seal, protects the wellhead drive assembly and sealing components from damage due to flushing pressures. The protector housing introduces a sealing ring adjacent the well end that seals around a tapered rod coupler of the polish rod when so lifted for preventing high flushing pressure from being exerted directly onto seal elements thereabove. As in the first embodiment, a polish rod seal can be fit to the housing for protecting a stuffing box portion of the wellhead assembly in addition to the sealing ring used for protection during flushing operations.

FIELD OF THE INVENTION

The present invention relates to improvements to sealing a polish rodfor a well. More particularly, apparatus is provided including a polishrod seal or is provided in addition to an existing stuffing box forbetter sealing the polish rod or for resisting high pressures such asthose applied in flushing operations.

BACKGROUND OF THE INVENTION

As the oilfield industry develops into the future, a major concern issafeguarding the environment. Oil companies are recognizing thatimprovements must be made in the process of extracting oil. Thisextraction must be completed with as little harm to the surroundingenvironment as possible.

As is well known to those in the in the industry, a pump stator, such asthe stator of a progressive cavity pump, is located downhole at the endof production tubing. A pump rotor engages the stator and is suspendedfrom at a distal end of a rod string. The rod string is driven fromsurface through a polish rod connected to a wellhead drive assembly forlifting well fluid to surface. The polish rod is connected to the rodstring extending downhole through a bottom-tapered rod coupler. Thepolish rod extends through a stuffing box to seal the rotating polishrod and well from the environment at surface. Typically very littlepressure is applied to the stuffing box. A progressive cavity pump issubject to plugging at or adjacent the stator and rotor. Fluids aresometime pumped downhole to flush debris from the pump.

One major concern is well fluid leaking onto the ground from prematurestuffing box failure; due to the high pressure being exerted on it whilethe well is being flushed. This flushing operation is done by pullingthe rotor out of the stator by lifting the polish rod to the top of itsbottom-tapered rod coupler. This allows the flush-by operation to thenback-flush the production tubing to remove sandy oil that is blockingthe free flow of oil. The pressure exerted onto the tubing is the samepressure exerted onto the stuffing box, which can reach levels of 2500psig.

In Canadian patents #2353277, #2027373, and #2171495 it clearly showsthat the main disadvantage in stuffing boxes is that they only sealaround the polish rod extending therethrough. During flushingoperations, greater force is exerted directly into the seal elements,which in turn causes the premature failure of the stuffing box.

What is needed is a device which aids in the longevity of existingstuffing boxes and greatly reduces the occurrence of well fluid leakingto atmosphere.

SUMMARY OF THE INVENTION

In one preferred embodiment, damage due to pressure exerted duringflushing is avoided and wellhead drive assembly seals protected througha housing positioned between the wellhead drive assembly and the well.The housing is universal in that it is independent of the type ofwellhead drive assembly or stuffing box; the housing need only beadapted to the polish rod. The housing introduces a sealing ring thatseals around a tapered rod coupler of the polish rod for preventing highpressure from being exerted directly onto seal elements thereaboveincluding whether the seal element are part of the housing or part ofthe wellhead drive assembly. Further, the housing spaces the wellheaddrive assembly from the well as needed. Advantageously, aflange-to-flange end design of the housing allows installation of thisdevice between any well flow tee of the well and the wellhead driveassembly.

In a broad aspect, apparatus is provided for sealing a polish rod belowa wellhead drive assembly connected to a well, the polish rod having atapered rod coupler at a bottom end, the apparatus comprising: a housinghaving a top end adapted for connection to the wellhead drive assemblyand a bottom end adapted for connection to the well, the housing havinga bore for passing the polish rod therethrough; and a sealing ringpositioned in the bore adjacent the bottom end, wherein when the polishrod is lifted to contact the tapered rod coupler with the sealing ringthe well is isolated from the top end of the housing.

The apparatus enables exercise of a method for sealing a polish rodbelow a wellhead drive assembly connected to a well while flushing thewell under pressure, the polish rod having a tapered rod coupler at abottom end, the method comprising: providing a housing between thewellhead drive assembly and the well the housing, the polish rod passingtherethrough and having a reduced diameter section of the bore adjacentthe housing's bottom end and sealing ring therebelow; lifting the polishrod to rest against the reduced diameter section and seal against thesealing ring; and applying pressure to the well for flushing the wellwherein the sealing ring protects the wellhead drive assembly from thepressure in the well.

In another aspect of the invention, a system is provided for sealing apolish rod in a well comprising: a wellhead drive assembly having apolish rod sealing stuffing box adapted for connection to the well andthe polish rod extending therethrough; a protector housing having a topend adapted for connection to the stuffing box and a bottom end adaptedfor connection to the well, the housing having a bore for passing thepolish rod therethrough; and a polish rod seal in the bore of thehousing, wherein the protector housing seals the polish rod before thepolish rod extends through the stuffing box.

In another aspect, the life of the stuffing box of any wellhead driveassembly can extended through the installation of a polish rod seal ofan embodiment of the invention. Where a wellhead drive assembly has astuffing box connected to a well and the stuffing box and well having astandard flange connection therebetween then apparatus can be employedcomprising: a housing having a bore for passing the polish rodtherethrough; a standard flange at a top end of the housing forconnection to the stuffing box of the wellhead drive assembly; astandard flange at a bottom end of the housing for connection to thewell; and a polish rod seal in the bore of the housing, wherein thepolish rod seal extends the longevity of the stuffing box.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of one embodiment of the housing for acylindrical through-bore stuffing box unit with universal flangedconnections; and

FIG. 2 illustrates greater detail of the internal components of the boreof the housing according to FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Having reference to FIG. 1, one embodiment of the universal pressureprotector 100 is shown comprising a housing 101 having a barrel 2, a topflange 1 and a bottom flange 3. The housing 101 is typically a one-piececylindrical through-bore steel unit with universal flanged designed endsresembling a dumbbell shape. A polish rod can extend through the housing101.

The universal pressure protector 100 is for use with an oil well thathas a rotary pump in which a polish rod is used to rotate the rotor of adown-hole pump on either a straight or slanted well. The housing 101 istypically mounted at surface between the top of a flow tee and thebottom end of a wellhead drive unit assembly. The wellhead drive unitassembly typically comprises an upper an existing stuffing box whichrestrains oil fluid leakage from the flow tee.

In one embodiment, the universal pressure protector 100 is an extenderon oil wells when more distance is needed between the flow tee andwellhead drive unit assembly.

The top flange 1, such as an industry standard RTJ R31 flanged end (ASMEB16.5 Class 300-8-bolt flange for nominal 3″ pipe), is bolted to thebottom of a stuffing box of an oil well drive unit (not shown). Theflange-to-flange design of a R31 type flange is capable of bolting underany current brand or type of wellhead drive unit assembly and flow teeor well that is used on a rotary drive oil well which is known toapplicant.

The barrel 2 has an outer thick wall of the through-bore barrel thathouses the inner parts of the universal pressure protector 100. Thebottom flange 3, a R31 flange designed end, is bolted to the top of anoil well flow tee (not shown). High-pressure grease nipple entriesallowing lubrication of tapered brass bushings, packing, and cavity.Through-bore grease nipples 4,5 grease the packing, brass mandrel andbottom-tapered bushing (See FIG. 2). A through-bore grease nipple 6greases the top-tapered brass bushing and fills the top sealed cavitylocated between the top of the housing 101 and the bottom flange of astuffing box.

The top and bottom flanges 1,3 are fit with inside threads 7,8respectively which allow lock-down rings 21,13 to be screwed therein.The flanges 1,3 are fit with eight bolt holes 9 which enable bolting ofthe device 100 to either the flow tee with the bottom flanged designedend 3, and the upper stuffing box with the top flanged designed end 1.

In more detail, with reference to FIG. 2, the inner part of thethrough-bore barrel 2 has a bore 23 where the polish rod slides through.The bore houses the sealing components of this embodiment comprising: asealing ring 11, a bottom threaded lock-down ring 12 and setscrew 13, abottom bushing 14 with wiper rings 15, grease mandrel 16, a firstplurality of packing rings 17, spring 18, a second plurality of packingrings 19, a top bushing 20, a top threaded lock-down ring 21 andsetscrew 22.

The bottom-tapered brass bushing 14 helps to centralize and stabilizethe polish rod. The top-tapered brass bushing 20 also helps tocentralize and stabilize the polish rod.

Teflon™ (trademark of Dupont) wiper rings 15 are recessed into thebottom-tapered brass bushing 14 which cleans off oil and sand from thepolish rod as it is being lifted through the through-bore barrel 2. Thebrass grease mandrel 16 allows grease to pass through and lubricatebetween the polish rod and bushings 20,14.

A first plurality of packing rings 17 and a second plurality of packingrings 19 seal around the polish rod. The first and second plurality ofpacking rings 17,19 are sandwiched between the top and bottom bushings20,14. A spring 18, when compressed, hold tension on these packing rings17, 19. The spring 18 can be positioned between the first and secondplurality of packing rings 17,19. The spring 18 is compressed when thethreaded lock-down ring 21 is threaded into the housing 101 and lockedwith setscrew 22 at the top of cylindrical through-bore barrel 2.

The threaded lock-down ring 21 is locked in with the setscrew 22.Further the top-tapered brass bushing 20 is also pushed down by the topthrough-bore threaded lock-down ring 21, compressing the spring 18 andpacking rings 17,19 that seal around the polish rod.

The bore 23 forms a relatively reduced diameter section 10 of thethrough-bore barrel 2. The bottom-reduced diameter section 10 ofthrough-bore 23 secures the bottom-tapered bushing 12 in saidthrough-bore 23.

This reduced diameter section 10 is the point where the bottom-taperedrod coupler of a polish rod comes to rest when lifted out of the oilwell production tubing in preparation for a flushing operation. Thisreduced diameter section 10 positions and stabilizes the bottom-taperedrod coupler of a polish rod during flushing operations and also keepsthe bottom-tapered rod coupler from coming in contact with thebottom-tapered brass bushing 14.

The sealing or rubber ring 11 seals around the top of the bottom-taperedrod coupler of the polish rod for sealing off oil fluid from enteringthe sealing elements thereabove during flushing operations. This rubberring 11 is held in place by the bottom threaded lock-down ring 12 whichhas a through-bore center and is locked with a setscrew 13.

Accordingly, in use, in preparation for a flushing operation, the polishrod is lifted to seal against the tapered rod coupler of the polish rod,thereby sealing the well from the wellhead drive assembly. When pressureresulting from the flush by operation is exerted on the well, any sealsabove the sealing ring, including the polish rod seals 19,17 and theexisting stuffing box of the wellhead drive assembly are protected. Thetapered rod coupler can rest against the reduced diameter section withthe tapered rod coupler sealing against the sealing ring.

When the housing is bolted to the upper stuffing box of a wellhead driveunit assembly a sealed cavity is formed. The cavity can be filled withgrease through the top grease nipple 6.

Within the oilfield industry is found many different types of corrosivematerials that will determine which types of materials are used to builda universal pressure protector 100. This enables the adaptation for useunder many unique conditions found throughout the oil fields. The outershell, or flanges 1,3 and barrel 2, can be made from many differenttypes and grades of steel. The tapered brass bushings 20,14, brassmandrel 16, grease nipples 4,5,6, inner spring 18, packing rings 17,19,Teflon™ rings 15, rubber ring 11, and lock-down rings 21,12 can all bemade from many different types of material. Further, the Teflon™ rings,rubber ring, tapered brass bushings, brass mandrel, and packing ringscan all be sized to fit any polish rod size.

The intended use of a Universal Pressure Protector is to protect wellequipment above the flow tee on an oil well, by absorbing the brunt ofthe tubing pressure that is exerted from the well pump. This UniversalPressure Protector can also be used as an extender on oil wells whenmore distance is needed between the flow tee and the wellhead driveunit.

1. Apparatus for sealing a polish rod below a wellhead drive assemblyconnected to a well, the polish rod having a tapered rod coupler at abottom end, the apparatus comprising: a housing having a top end adaptedfor connection to the wellhead drive assembly and a bottom end adaptedfor connection to the well, the housing having a bore for passing thepolish rod therethrough; and a sealing ring positioned in the boreadjacent the bottom end, wherein when the polish rod is lifted tocontact the tapered rod coupler with the sealing ring the well isisolated from the top end of the housing.
 2. The apparatus of claim 1further comprising: a reduced diameter section of the bore adjacent thehousing's bottom end for retaining a polish rod seal in the borethereabove and for forming a point against which the tapered rod couplercomes to rest when the polish rod is lifted; and wherein the sealingring is positioned below the reduced diameter section.
 3. The apparatusof claim 2 wherein the polish rod seal further comprises a top bushing,a bottom bushing and packing rings therebetween.
 4. The apparatus ofclaim 3 wherein the bottom bushing is supported on the reduced diametersection of the bore.
 5. The apparatus of claim 1 wherein the sealingring is secured in the bottom end of the housing with a lock-down ring.6. The apparatus of claim 3 wherein the top bushing is secured in thetop end of the housing with a lock-down ring.
 7. The apparatus of claim3 wherein packing rings further comprise: a first plurality of packingrings; a second plurality of packing rings; and a spring positionedtherebetween.
 8. The apparatus of claim 3 wherein the top bushing issecured in the top end of the housing with a lock-down ring.
 9. Theapparatus of claim 8 wherein the lock-down ring is threaded into the topend of the housing for compressing the spring.
 10. The apparatus ofclaim 3 wherein the bottom bushing further comprises wiper rings forcleaning the polish rod.
 11. The apparatus of claim 1 wherein thehousing extends the wellhead drive assembly a greater distance above thewell.
 12. A system for sealing a polish rod in a well comprising: awellhead drive assembly having a polish rod sealing stuffing box adaptedfor connection to the well and the polish rod extending therethrough; aprotector housing having a top end adapted for connection to thestuffing box and a bottom end adapted for connection to the well, thehousing having a bore for passing the polish rod therethrough; and apolish rod seal in the bore of the housing, wherein the protectorhousing seals the polish rod before the polish rod extends through thestuffing box.
 13. The system of claim 12 wherein the polish rod hastapered rod coupler at a bottom end and the polish rod seal furthercomprises: a top bushing, a bottom bushing and packing ringstherebetween; a reduced diameter section of the bore adjacent thehousing's bottom end for retaining the bottom bushing in the borethereabove and for forming a point against which the tapered rod couplercomes to rests when the polish rod is lifted; and a sealing ringpositioned in the bore adjacent the bottom end, wherein when the polishrod is lifted to contact the tapered rod coupler with the sealing ringthe well is isolated from the top end of the housing.
 14. The system ofclaim 13 wherein packing rings further comprise: a first plurality ofpacking rings; a second plurality of packing rings; and a springpositioned therebetween.
 15. The system of claim 14 wherein the topbushing is adjusted relative to the top end of the housing forcompressing the spring.
 16. The system of claim 12 wherein the housingis extends the wellhead drive assembly a greater distance above thewell.
 17. A method for sealing a polish rod below a wellhead driveassembly connected to a well while flushing the well under pressure, thepolish rod having a tapered rod coupler at a bottom end, the methodcomprising: providing a housing between the wellhead drive assembly andthe well, the polish rod passing therethrough and having a reduceddiameter section of the bore adjacent the housing's bottom end andsealing ring therebelow; lifting the polish rod to rest the tapered rodcoupler against the reduced diameter section and seal against thesealing ring; and applying pressure to the well for flushing the wellwherein the sealing ring protects the wellhead drive assembly from thepressure in the well.
 18. The method of claim 17 wherein the wellheaddrive assembly has a polish rod sealing stuffing box adapted forconnection to the well and the polish rod extending therethrough, themethod further comprising: connecting the housing to the stuffing box;and when the polish rod is lifted, protecting the stuffing box from thepressure in the well.
 19. The method of claim 18 wherein the housingfurther has a polish rod seal, the method further comprising: sealingthe well from the stuffing box at the polish rod seal; and when thepolish rod is lifted, protecting the polish rod seal and the stuffingbox from the pressure in the well.
 20. Apparatus for sealing a polishrod below a wellhead drive assembly having a stuffing box connected to awell, the stuffing box and well having a standard flange connectiontherebetween, the apparatus comprising: a housing having a bore forpassing the polish rod therethrough; a standard flange at a top end ofthe housing for connection to the stuffing box of the wellhead driveassembly; a standard flange at a bottom end of the housing forconnection to the well; and a polish rod seal in the bore of the housingprotecting the stuffing box from pressure in the well.
 21. The apparatusof claim 20 further comprising: a bottom bushing retained in the bore ofthe housing; a top bushing; and wherein the polish rod seal ispositioned therebetween.
 22. The apparatus of claim 20 wherein thepolish rod seal comprises packing rings.
 23. The apparatus of claim 22wherein packing rings further comprise: a first plurality of packingrings; a second plurality of packing rings; and a spring positionedtherebetween.
 24. The apparatus of claim 21 wherein the top bushing issecured in the top end of the housing with a lock-down ring.
 25. Theapparatus of claim 24 wherein the lock-down ring is threaded into thetop end of the housing for compressing the spring.
 26. The apparatus ofclaim 21 wherein the bottom bushing further comprises wiper rings forcleaning the polish rod.
 27. The apparatus of claim 20 wherein thepolish rod has a tapered rod coupler at a bottom end of the polish rod,the apparatus further comprising: a sealing ring positioned in the boreadjacent the bottom end of the housing, wherein when the polish rod islifted to contact the tapered rod coupler with the sealing ring the wellis isolated from the top end of the housing.
 28. The apparatus of claim27 wherein the sealing ring is secured in the bottom end of the housingwith a lock-down ring.
 29. The apparatus of claim 27 wherein: thereduced diameter section of the bore adjacent the housing's bottom endforms a point against which the tapered rod coupler comes to rest whenthe polish rod is lifted, and the sealing ring is positioned below thereduced diameter section.
 30. The apparatus of claim 20 wherein thehousing extends the wellhead drive assembly a greater distance above thewell.